RELAPSING FEVER 105 



on a relapsing fever patient and were afterwards, 

 under certain conditions, crushed and rubbed into 

 a scratched surface of the skin of a healthy man 

 or animal, the latter will develop the disease. 

 The parasite is equally able to pass through the 

 unbroken moist membranes of the body such as 

 the eye and the inside of the nose. The dissection 

 of the lice which had fed on the infected blood 

 showed that the spirochaetes in the gut become 

 rapidly immobile, appear to degenerate, and 

 within twenty-four hours have all disappeared. 

 For the next seven days no spirochaetes can be 

 found in the louse. About the eighth day they 

 reappear in the coelomic cavity, that is, the space 

 between the gut and the body wall. This phe- 

 nomenon takes place in about 20 per cent of the 

 lice which have taken the infecting feed. The 

 parasites are at first very small and thin, but 

 they grow to that size which they develop in the 

 blood of man. By the twentieth day from that 

 on which they fed on the relapsing fever patient 

 they have all again disappeared. Throughout 

 this period a person may feed the infected lice on 

 himself with impunity, as the bite of the insect 

 is harmless. For the disease to be caused the 

 louse must be crushed so as to release the para- 

 sites which are contained in the body of the 

 insect and which do not appear to pass out unless 

 its skin is broken. A man therefore inoculates 

 himself with the disease by scratching the bites 

 and at the same time crushing the louse. The 



